title: Distinct structural elements dictate the specificity of the type III pentaketide synthase from Neurospora crassa.
abstract: The fungal type III polyketide synthase 2'-oxoalkylresorcylic acid synthase (ORAS) primes with a range of acyl-Coenzyme A thioesters (C4-C20) and extends using malonyl-Coenzyme A to produce pyrones, resorcinols, and resorcylic acids. To gain insight into this unusual substrate specificity and product profile, we have determined the crystal structures of ORAS to 1.75 A resolution, the Phe-252-->Gly site-directed mutant to 2.1 A resolution, and a binary complex of ORAS with eicosanoic acid to 2.0 A resolution. The structures reveal a distinct rearrangement of structural elements near the active site that allows accommodation of long-chain fatty acid esters and a reorientation of the gating mechanism that controls cyclization and polyketide chain length. The roles of these structural elements are further elucidated by characterization of various structure-based site-directed variants. These studies establish an unexpected plasticity to the PKS fold, unanticipated from structural studies of other members of this enzyme family.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 600 S. Mathews Avenue, Urbana, IL 61801, USA.
authors.forename: Sheryl B
authors.initials: SB
authors.lastname: Rubin-Pitel
authors.forename: Houjin
authors.initials: H
authors.lastname: Zhang
authors.forename: Trang
authors.initials: T
authors.lastname: Vu
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Brunzelle
authors.forename: Huimin
authors.initials: H
authors.lastname: Zhao
authors.forename: Satish K
authors.initials: SK
authors.lastname: Nair
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D017930:Genes, Reporter / Q000235:genetics; D018942:Macrolides / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009492:Neurospora crassa / Q000201:enzymology*; D048630:Polyketide Synthases / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D018942:Macrolides; D048630:Polyketide Synthases